The leatherback turtle (Dermochelys coriacea) is a remarkable marine reptile, tracing its lineage back to the age of dinosaurs. It is the largest living turtle species, distinguished by a unique, leathery outer shell rather than a hard, bony one. Its presence in marine ecosystems makes it a subject of considerable scientific and conservation interest. The species’ distinct appearance and widespread oceanic presence make it easily recognizable among sea turtles.
Distinctive Features
The leatherback turtle possesses several unique physical characteristics that set it apart from other sea turtle species. Its carapace, unlike the hard shells of other turtles, is composed of small, interlocking dermal bones beneath a tough, rubbery skin, giving it a leathery texture. This flexible carapace features seven prominent ridges running lengthwise, tapering to a blunt point at the rear.
Leatherbacks are the largest turtles, with some individuals reaching impressive sizes. They can weigh over 600 kilograms (1,300 pounds) and measure up to 2.2 meters (7.2 feet) in length. Their immense size plays a role in their ability to regulate body temperature, a unique adaptation among reptiles that allows them to thrive in colder waters. This thermoregulation, often referred to as gigantothermy, involves a combination of large body mass, a thick layer of fat and oily connective tissue, and adjustments in blood flow. Their powerful, elongated front flippers, proportionally longer than those of other sea turtles, lack claws and scales. Their paddle-shaped back flippers further enhance their streamlined body, enabling efficient movement across vast oceanic distances.
Global Wanderers
Leatherback turtles are renowned for their extensive migratory journeys, covering thousands of miles across the world’s oceans each year. These journeys link their tropical and subtropical nesting beaches with distant foraging grounds in temperate and even sub-polar waters. Some individuals have been tracked swimming over 16,000 kilometers (10,000 miles) annually, with one recorded traveling over 20,500 kilometers (12,700 miles) from New Guinea to Oregon.
Their ability to withstand a wide range of water temperatures, from warm tropical seas to cooler northern latitudes, is a testament to their unique physiological adaptations for thermoregulation. Leatherbacks are also exceptional divers, capable of descending to remarkable depths. They have been recorded diving nearly 1,200 meters (4,000 feet), deeper than most marine mammals, often in pursuit of their prey. While primarily pelagic, they are also known to forage in coastal waters.
Specialized Diet
Leatherback turtles exhibit a highly specialized diet, primarily consuming soft-bodied invertebrates, with jellyfish and salps forming the bulk of their sustenance. This dietary preference has led to unique adaptations in their oral and pharyngeal anatomy. Their mouths are equipped with pointed cusps and sharp-edged jaws, which are distinct from the chewing or tearing jaws found in other sea turtles.
A notable adaptation is the presence of backward-pointing spines, or papillae, lining their mouth and throat. These spines help secure slippery jellyfish, preventing them from escaping once captured. Despite the low energy content of jellyfish, leatherbacks consume them in large quantities, often needing to eat a significant amount relative to their body size to meet their energy needs for reproduction and long migrations. By preying on jellyfish, leatherback turtles play a role in regulating jellyfish populations within marine ecosystems.
Protecting Their Future
Leatherback turtle populations face various threats, leading to their classification as Vulnerable to Critically Endangered by the International Union for Conservation of Nature (IUCN), with Pacific populations being particularly at risk. Incidental capture in fishing gear, known as bycatch, represents a major global threat. Leatherbacks often become entangled or hooked in pelagic longline fisheries, gillnets, and trawl nets, leading to injury or drowning.
Plastic pollution poses another significant danger, as leatherbacks frequently mistake floating plastic bags for jellyfish, leading to ingestion and potentially fatal blockages. Habitat loss and degradation at nesting sites also contribute to their decline. Coastal development, shoreline armoring, and artificial lighting on beaches can deter nesting females and disorient hatchlings. Climate change further impacts nesting beaches through rising sea levels, coastal erosion, and altered sand temperatures, which can affect the sex ratio of hatchlings. Conservation efforts are underway globally, including bycatch reduction devices in fisheries and protecting nesting habitats, to help ensure the survival of these ancient mariners.